In 3 Nephi chapter 16 the Savior gave the Nephites an encapsulated view of what would follow in the next 2000+ years. Like most prophecies of such a wide scope, this one is best understood from hindsight. As we read it, the Christian apostasy that followed the Savior’s death is not difficult to recognize. We can also see references to the European conquest and colonization of the Americas and then the restoration of the gospel. We recognize those events because they are in our past but the events he mentioned that are still in our future are much more difficult.
The outline the Savior gave is kind of a catalog that creates a chronological pattern. The pattern is more easily seen from a distance than up close. That is, one can get a better notion of the Savior’s message if it is read as an entire picture rather than in its individual units. That is also true of most prophecies that describe a whole series of events. For example, Nephi’s tree of life vision covers those same 2000+ years, but he includes enough detail that it is relatively easy for us to understand—again from hindsight where we can attach known events to his predictions. The first few verses of Isaiah 2 seem easy enough but after that it doesn’t fit our hindsight so we have to take its story out of chronological order so it will fit our preconceived pattern. Isaiah 49 paints a beautiful picture of the restoration of the gospel and the temple, and then the gathering of Israel. Jacob 5 and Revelation cover those same 2000 years. They paint interesting pictures but it is difficult to attach events to most of their individual parts.
For those who were contemporary with the prophets who made the prophecies, who did not have the advantage of hindsight, interpreting them would have been more difficult than it is for us. For that reason it seems apparent that the prophecies were not intended to be so much descriptions of future chronological events as they were testimonies that everything was already fore-known by God and that nothing will frustrate his designs. Therefore in the end everything will turn out just right.
3 Nephi 16 is very much like that. Its purpose seems to be to paint a beautiful and encouraging picture to demonstrate that there is a God in Heaven who is in charge. And in the end he will make sure that those who are faithful to their covenants will come off triumphantly. But in the meantime, he will also permit all people (both the good and the bad) to be in an environment that gives them the opportunity to choose how they will define their own eternal nature by whether they disdain, appreciate, or love other people. (I think those attitudes pretty much map to the three degrees of glory.)